The purpose of the proposed research is to evaluate the differential validity of a related set of procedures and measurements designed to measure the older infant's ability to detect categories in visual information. The basic strategy involves selection of two categories which, on an a priori basis, infants 14 to 15 months old should possess or be able to extract. By comparing the child's reactivity in several response domains across varied procedures used to test the child's conceptual knowledge it should be possible to arrive at conclusions regarding the relative sensitivity of the different procedures for different profiles of response. These results should be of value to investigators concerned with the young child's acquisition of knowledge.